This invention relates to a new group of polymerizable oligomers, and more particularly, to oligourethanacrylates, to the methods for preparing them and to polymers on the basis thereof.
It is a commonly known that polyurethanes are very important materials in the manufacture of various polymers and articles.
Owing to a unique combination of high physico-chemical properties, good resistance to attrition, stability against the action of many solvents, oxidants, water, oils and fuels, exhibiting high adhesion strength with respect to various materials, and many other valuable properties, polyurethanes are used on an ever increasing scale in the manufacture of elastomers, foams, protective coatings, glues, sealing compounds and other polymeric materials.
The range of starting materials that can be used in the manufacture of polyurethanes is quite numerous, and this makes it possible to prepare polyurethanes having varied structures and different number of cross links, with varying flexibility of its macromolecules, high character for the intermolecular interaction, and to prepare materials possessing desired properties.
The method most widely used in the manufacture of polyurethanes is based on the polycondensation reaction between low-molecular or oligomeric di- or polyisocyanates and alkyleneglycols of carbon- or heterochain diols or polyols of various structures.
If bifunctional components are used, polyurethanes of linear structure are formed. The increasing number of functional groups to three or more results in branched or reticulate polyurethanes.
The formation of polyurethanes by the above method proceeds according to the mechanism of migration polymerization.
Known in the prior art are methods for preparing reticulate polyurethanes, consisting of joining the reaction of interaction between isocyanates and glycols or their monosubstituted derivatives with the reaction of radical polymerization of vinyl compounds, which ensure increased thermal stability and improves some mechanical properties of the polymers.
According to the above-mentioned methods for preparing reticulate polyurethanes, the first oligomeric compounds containing urethane groups and unsaturated polymerizable groups are synthesized, for example, by the interaction between oligoetherglycols and oligoesterglycols or oligodienediols with diisocyanates and monometacrylic ether of ethyleneglycol, or by the interaction between oligoglycols with vinyl monomers containing isocyanate group. The thus prepared oligomeric compounds are then polymerized according to the radical mechanism with the formation of polyurethanes having reticulate structure.
The main disadvantage of the above-mentioned methods for preparing polyurethanes is the use of isocyanates which are necessary to form urethane bonds.
The formation of urethane along with the use of isocyanates is usually accompanied by side reactions which produce allophanic and biuret groups possessing low stability with respect to temperatures and oxidation, and incapable of bearing stress, and hence impairing the properties of polyurethanes.
Most aliphatic and aromatic isocyanates are toxic compounds and therefore special precautions should be taken because of their high volatility.
A restricted number of representatives of the aliphatic and aromatic isocyanates produced on an industrial scale makes it impossible to vary widely the structure, and hence, the properties of the polyurethanes produced on their basis.
Moreover, the methods for preparing isocyanates having practical importance, are labour-consuming and consist of several steps (for example, the separation and purification of the isomers in the synthesis of toluylenediisocyanates) which raises the cost of these products.
The object of this invention is to work out new polymerizable oligomeric compounds containing in their molecules urethane groups without using isocyanates.
Another object of this invention is to rule out the formation of undesirable unstable allophanic and biuret bonds in the synthesized oligourethanacrylates, which improves significantly the service characteristics of polyurethanes on their basis.
Another object of this invention is also the preparation of oligourethanes on the basis of less toxic, cheaper and more available starting products.
Still another object of the invention is to prepare polymers having a three-dimensional reticulate structure having valuable physico-mechanical properties on the basis of the synthesized liquid and the crystalline oligourethanacrylates of various structure.
These and other objects and advantages of this invention will become clear from the description which follows hereinafter.
The said objects have been attained in polymerizable oligourethanacrylates characterized according to the invention by the following general formula: ##STR4## where ##STR5## is a radical of a telogen which is:
(a) a chloroformiate of monoesters of alkyleneglycols and acids of the acrylic series, a chloroformiate of monoesters of bis-phenols and acids of the acrylic series;
(b) monoaminoalkyl ester of acrylic acid,
N-substituted monoaminoalkyl ester of acids of the acrylic series;
x is H, CH.sub.3 or a halide;
R is a radical of glycol bis-phenol or amino alcohol;
U is an urethane group having the structure
(a) ##STR6## if the telogen contains the --N(Y)-H functional group; or
(b) ##STR7## if, the telogen contains the ##STR8## functional group;
Y is a substitute at the nitrogen atom of the telogen, which is a hydrogen atom, or an aryl radical;
Z is a substitute at the nitrogen atom of the aliphatic polyamine, and may be a hydrogen atom, alkyl radical or aryl radical;
R' is a radical of aliphatic polyamine, an N-substituted radical of the aliphatic polyamine containing from 2 to 10 carbon atoms, a radical of polyamine having the formula: ##STR9## where:
M is CH.sub.2 ; O; S; SO.sub.2 ; NH;
M' is CH.sub.2 or O;
R" is a radical of a polyol containing an aliphatic hydrocarbon radical containing from 2 to 10 atoms of carbon, a radical of bis-phenol, a radical of polyalkyl oligoester;
R'" is R', if the telogen contains the ##STR10## functional group;
R'" is R", if the telogen contains the --N(Y)H functional group;
n is a number characterizing the degree of polycondensation of oligourethanacrylate equal to zero, unity or a whole number greater than unity. The said polymerizable oligourethanacrylates have been prepared by the method according to the invention consisting in carrying out the reaction of a non-equilibrium polycondensation of polyol chloroformiates with polyamines and telogens selected from the group consisting of chloroformiates of monoesters of alkylglycols and acids of the acrylic series, chloroformiates of monoesters of bis-phenols and acids of the acrylic series, monoaminoalkyl esters of the acids of the acrylic series, with a simultaneous or step-wide introduction of the reactants into the reaction mixture in the presence of acceptors of hydrogen chloride which is evolved in the reaction.